TORONTO — In Steve McQueen’s “12 Years a Slave,” Solomon Northop, a free man from upstate New York who’s kidnapped and sold into slavery in Louisiana played by Chiwetel Ejiofor, is hung for daring to strike an abusive and imbecilic plantation hand (Paul Dano). He’s cut down, but only just barely enough to reach the ground. McQueen captures it all in one long, agonizing take, as Northop is left dangling, shuffling excruciatingly on his tiptoes.

“I don’t think I’ve seen that on film, and I wanted to make damn sure if it was on film, it was going to be done well,” McQueen said in a recent interview. “It was very necessary for me to use those kind of shots to tell the story. Film is what 115, 120 years old? It’s a baby. There’s no right or wrong way to shoot anything. It’s not style. It’s necessity.”

Film history, however, is long enough that one might expect one of the nation’s most essential chapters to have been depicted on screen more frequently and fervently. “It’s a massive hole,” says McQueen. There have, of course, been a handful of notable films about slavery (“Beloved,” “Amistad,” the miniseries “Roots”), but, it’s safe to say, never before has there been a movie like this. “12 Years a Slave” is the most unblinking portrait of slavery yet seen in cinema: a straightforward resurrection of its atrocities, complications and, most of all, its plain reality.

“I wanted everyone to be Solomon Northup,” says McQueen. “You are on that journey with him.”

“12 Years a Slave,” which Fox Searchlight will release in theaters Oct. 18, premiered over the weekend at the Toronto International Film Festival where it was hailed as a masterpiece and very possibly this year's best picture Oscar winner. It is quickly gathering force as a kind of epochal achievement.

McQueen, the British director of the sex-addiction drama “Shame” and the Irish Republican Army hunger strike tale “Hunger,” had planned to make a film about slavery, but it didn’t take shape until his wife came across Northop’s 1853 autobiography, which straightforwardly tells of his nightmarish odyssey.

Ejiofor (the “Dirty Pretty Things,” “Kinky Boots” British actor of Nigerian roots) plays Northop, a violinist taken from his family and put into servitude on plantations, all the while unable to contact his home or even proclaim his true identity. His journey, “down the rabbit hole” as Ejiofor says, isn’t into a uniformly evil world of slavery, but one peopled by a wide spectrum of human decency, both masters and slaves.

It’s in many ways about how, faced with unspeakable hardship, one reacts. Northop refuses to surrender.

“They’re something about it that I find very heroic,” says Ejiofor. “You could only find that by really confronting his experience head-on.”

The hanging scene is only one of the film’s lengthy moments — a beating that serves as an introduction to life as a slave; a forced whipping of another slave — showed in full, unbroken view.

“If you don’t know what that feels like,” says Ejiofor, “if you don’t get inside that experience of being there all day, out there in the sun, hung by your neck, barely able to stay alive, then you don’t know the depth that this man is prepared to go to in order to keep himself alive.”

The film is often harrowingly difficult to watch. But it’s ultimately concerned with being faithful to Northop’s experience (“Solomon deserved nothing less,” says McQueen), and capturing his undimmed dignity. Northop went on to be part of the abolitionist movement and lecture on slavery throughout the Northeast.

“This is not National Geographic or any kind of scientific exploration to tell you how things actually were,” says McQueen. “It’s about the narrative.”

Though the experience of making such a film, shot in 35 days outside of New Orleans, might be expected to be weighed with the heaviness of its subject, the cast says the process was too focused, too fast-moving for such a mindset. Says McQueen: “If you start thinking about it in such a way, it will paralyze you.”

Michael Fassbender, who starred in both of McQueen’s previous films, plays Edwin Epps, the far harsher of two plantation owners. (The other, more benevolent plantation owner is played by Benedict Cumberbatch). He’s described with understatement as “a man of hard countenance.”

Fassbender sought to find the humanity in Epps, who’s torn by his love for his most prized cotton-picker (Lupita Nyong’o, in a shattering performance).

“You are going to places that are uneasy, but it’s my job,” says Fassbender. “Of course the emotional elements follow, and they do have an effect and there’s a residue going home with them. But concentrating on the work sort of protects yourself from that.”

The film, made with a budget of $22 million, was produced by Brad Pitt’s production company Plan B, and the actor appears in a small but pivotal role, warning Epps of a coming “day of reckoning.” Speaking to reporters at Toronto, he expressed his deep pride in having been a part of “12 Years a Slave.”

“If I never get to participate in a film again ...” he said, trailing off. “This is it for me.”